Milling machine are used in a variety of applications including removing material off a ground surface, stabilizing soil, surface mining, and mixing milled materials into a ground surface, among other things. These milling machines include rotary mixers and cold planers. Rotary mixers, in particular, are used to pulverize a ground surface, such as roadways based on asphalt, and mix a resulting pulverized layer with an underlying base, to stabilize the ground surface. Rotary mixers may also be used as a soil stabilizer to cut, mix, pulverize, and stabilize a soil surface, for attaining a strengthened soil base. Optionally, rotary mixers may add asphalt emulsions or other binding agents during pulverization to create a reclaimed surface.
A rotary mixer includes a frame, lifting columns that alter the height of the frame relative to the ground surface, a mixing chamber, and a rotor within the mixing chamber that is also height adjustable. The mixing chamber also includes a front door and a rear door. The front door and the rear door are used to control the amount of material entering the mixing chamber, the amount of material leaving the mixing chamber, and the degree of pulverization of the material within the mixing chamber, among other things.
On a worksite, a rotary mixer will typically perform multiple milling passes over a work area. To perform a milling pass, an operator generally executes a sequence of operations involving positioning the machine frame, the rotor, the front door, and the rear door to desired positions. These components are controlled by separate operator initiated control commands. After the completion of a milling pass, the rotary mixer typically needs to be repositioned before it can commence another milling pass. During maneuvering, the rotary mixer operator will generally reposition the machine frame, the rotor, the front door, and the rear door. When the rotary mixer is in position for the second milling pass, the operator will again move the frame, the rotor, the front door, and the rear door to the desired milling positions.
Manually controlling these functions may result in inconsistent transitions and increasing the time necessary to prepare a work site. Separately controlling each function may also be cumbersome for the operator and may reduce productivity.
U.S. Pat. No. 8,424,972 ('972 reference) discloses a control device automatically controlling a lifting operation of at least one rear and/or front lifting column to position the machine frame parallel to ground using sensors. The control device of the '972 reference controls the machine frame at a predetermined milling level, parallel to the ground. However, the '972 reference fails to discuss providing a simplified transition between different rotary mixer operating modes.